The Assembly History of Field Spheroidals: Evolution of Mass-to-light Ratios and Signatures of Recent Star Formation

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dc.creatorTreu, T.
dc.creatorEllis, R. S.
dc.creatorLiao, T. X.
dc.creatorvan Dokkum, P. G.
dc.creatorTozzi, P.
dc.creatorCoil, A.
dc.creatorNewman, J.
dc.creatorCooper, M.
dc.creatorDavis, M.
dc.date2005-03-07
dc.date.accessioned2026-07-07T10:27:25Z
dc.date.available2026-07-07T10:27:25Z
dc.descriptionWe present a comprehensive catalog of high signal-to-noise spectra obtained with the DEIMOS spectrograph on the Keck II telescope for a sample of F850LP<22.43 (AB) field spheroidal (E+S0s; 163) and bulge dominated disk (61) galaxies in the redshift range 0.2<z<1.2. We examine the zero point, tilt and scatter of the Fundamental Plane (FP) as a function of redshift and morphological properties, carefully accounting for luminosity-dependent biases via Montecarlo simulations. The evolution of the overall FP can be represented by a mean change in effective mass-to-light ratio given by <d \log (M/L_{\rm B})/dz>=-0.72^{+0.07}_{-0.05}\pm0.04. However, this evolution depends significantly on the dynamical mass, being slower for larger masses as reported in a previous letter. In addition, we separately show the intrinsic scatter of the FP increases with redshift as d(rms(M/L_{\rm B}))/dz=0.040\pm0.015. Although these trends are consistent with single burst populations which formed at $z_f>2$ for high mass spheroidals and z_{f}~1.2 for lower mass systems, a more realistic picture is that most of the stellar mass formed in all systems at z>2 with subsequent activity continuing to lower redshifts (z<1.2). The fraction of stellar mass formed at recent times depend strongly on galactic mass, ranging from <1% for masses above 10^{11.5} M_{\odot} to 20-40% below 10^{11} M_{\odot}. Independent support for recent activity is provided by spectroscopic ([\ion{O}{2}] emission, Hδ) and photometric (blue cores and broad-band colors) diagnostics. Via the analysis of a large sample with many independent diagnostics, we are able to reconcile previously disparate interpretations of the assembly history of field spheroidals. [Abridged]
dc.description26 pages including 24 figures, submitted to ApJ. Complete and compact version with full resolution images available at http://www.astro.ucla.edu/~ttreu/ms.pdf
dc.identifierhttps://arxiv.org/abs/astro-ph/0503164
dc.identifierhttp://arxiv.org/abs/astro-ph/0503164
dc.identifierAstrophys.J.633:174-197,2005
dc.identifierdoi:10.1086/444585
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/177147
dc.subjectAstrophysics
dc.titleThe Assembly History of Field Spheroidals: Evolution of Mass-to-light Ratios and Signatures of Recent Star Formation
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